Kinematics of the RRR, RRT (Passive) and RRRR, RRRT (Active) Linkage-Mechanism Building Blocks With Applications and Reporting of New Findings

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
P. A. Simionescu
Keyword(s):  
Closed Form ◽  
Building Blocks ◽  
Linkage Mechanism ◽  
Deployable Structures ◽  
Optimum Synthesis ◽  
New Findings

Abstract Closed-form equations for the analyses of the RRR and RRT (passive) and of the RRRR and RRRT (active) kinematic building blocks are presented in the paper. Implementations of these equations in computer subroutine are then discussed. Applications chosen to illustrate the usefulness of these subroutines include optimum synthesis of a function-generating mechanism, deployable structures, radial engines, a tire-curing press, and the concomitant simulation of four-bar and crank-slider coupler cognates. For the latter, properties not yet reported have been revealed through numerical experimentations.

scholarly journals From Gaze Perception to Social Cognition: The Shared-Attention System

2021 ◽  
pp. 174569162095377
Author(s):  
Lisa J. Stephenson ◽  
S. Gareth Edwards ◽  
Andrew P. Bayliss
Keyword(s):  
Social Cognition ◽  
Building Blocks ◽  
Mental States ◽  
Evaluation Agency ◽  
Gaze Following ◽  
Gaze Perception ◽  
Shared Attention ◽  
New Findings ◽  
Attention System ◽  
Sas Model

When two people look at the same object in the environment and are aware of each other’s attentional state, they find themselves in a shared-attention episode. This can occur through intentional or incidental signaling and, in either case, causes an exchange of information between the two parties about the environment and each other’s mental states. In this article, we give an overview of what is known about the building blocks of shared attention (gaze perception and joint attention) and focus on bringing to bear new findings on the initiation of shared attention that complement knowledge about gaze following and incorporate new insights from research into the sense of agency. We also present a neurocognitive model, incorporating first-, second-, and third-order social cognitive processes (the shared-attention system, or SAS), building on previous models and approaches. The SAS model aims to encompass perceptual, cognitive, and affective processes that contribute to and follow on from the establishment of shared attention. These processes include fundamental components of social cognition such as reward, affective evaluation, agency, empathy, and theory of mind.

A Hexagonal Prism Folding for Membrane Packaging Based on Concepts of Finite Rigid Motion and Kinematic Synthesis

2016 ◽  
Author(s):  
Kassim Abdul-Sater
Keyword(s):  
Spatial Configuration ◽  
Rigid Motion ◽  
Building Blocks ◽  
Computational Procedure ◽  
Hexagonal Prism ◽  
Linkage Mechanism ◽  
Space Applications ◽  
Kinematic Synthesis ◽  
Kinematic Chains ◽  
Position Synthesis

This paper discusses the use of concepts of finite rigid body kinematics as well as kinematic synthesis in non-rigid, engineering folding problems. The exemplary task consists in designing a folding pattern, which allows to fold a circular sheet from a flat unfolded state into a prescribed compact spatial configuration that forms a hexagonal prism. Other two-configuration design problems may be found for instance in space applications where membranes in tensegrity reflector antennas need to be stowed in a spacecraft. The folding motion could be actuated using an appropriately designed linkage mechanism attached to the membrane, which, however, is not considered in this paper. The specific result of this work is a creative but systematic and computational procedure for crease pattern design. The approach is essentially based on the relative kinematics equations of serial kinematic chains and the finite position synthesis of linkage building blocks. These techniques sucessively combine to segment a flat bounded surface, such that it can reach the prescribed spatial configuration.

scholarly journals FlhA Undergoes Cyclic Open-close Domain Motions During Flagellar Protein Export in Salmonella

2021 ◽  
Author(s):  
Tohru Minamino ◽  
Yumi Inoue ◽  
Miki Kinoshita ◽  
Akio Kitao ◽  
Keiichi Namba
Keyword(s):  
Closed Form ◽  
Protein Transport ◽  
Building Blocks ◽  
Protein Export ◽  
Side Chain ◽  
Transport Activity ◽  
Flagellar Assembly ◽  
Flagellar Protein ◽  
Domain Motions

Abstract The flagellar type III secretion system (fT3SS) transports flagellar building blocks from the cytoplasm to the distal end of the growing flagellar structure. The C-terminal cytoplasmic domain of FlhA (FlhAC) serves as a docking platform for flagellar chaperones in complex with their cognate substrates and ensures the strict order of protein export for efficient flagellar assembly. FlhAC adopts open and closed conformations, and the chaperones bind to the open form, allowing the fT3SS to transport the substrates to the cell exterior. To clarify the role of the closed form in flagellar protein export, we isolated pseudorevertants from the flhA(G368C/K549C) mutant, in which the closed conformation is stabilized to inhibit the protein transport activity of the fT3SS. Each of M365I, R370S, A446E and P550S substitutions in FlhAC identified in the pseudorevertants affected hydrophobic side-chain interaction networks in the closed FlhAC structure, thereby restoring the protein transport activity to a considerable degree. We propose that a cyclic open-close domain motion of FlhAC is required for rapid and efficient flagellar protein export where a structural transition from the open to the closed form induces the dissociation of empty chaperones from FlhAC.

Experimental Development of Self-Deployable Structures

1998 ◽  
Vol 13 (3) ◽  
pp. 157-169
Author(s):  
Depankar Neogi ◽  
Craig Douglas ◽  
David R. Smith
Keyword(s):  
Research Effort ◽  
Research Work ◽  
Building Blocks ◽  
The Self ◽  
Structural Element ◽  
Deployable Structures ◽  
Experimental Development ◽  
Deployable Structure ◽  
New Family ◽  
Standing Structure

Deployable space structures are prefabricated structures which can be transformed from a closed, compact configuration to a predetermined expanded form in which they are stable and can bear loads. The present research effort investigates a new family of deployable structures, called self-deployable structures. Unlike other deployable structures, which have rigid members and moving joints, the self-deployable members are flexible while the connecting joints are rigid. The joints store the predefined geometry of the deployed structure in the collapsed state. The self-deployable structure is stress-free in both deployed and collapsed configurations and results in a self-standing structure which acquires its structural properties after a chemical reaction. Reliability of deployment is one of the most important features of the self-deployable structure, since it does not rely on mechanisms that can lock during deployment. The unit building block of these structures is the self-deployable structural element. Several of these elements can be linked to generate more complex building blocks such as a triangular or tetrahedral structures. Different self-deployable structural element and self-deployable structure concepts are investigated in the present research work, and the performance of triangular and tetrahedral prototype structures are experimentally explored.

scholarly journals Wallpaper group kirigami

2021 ◽  
Vol 477 (2252) ◽  
pp. 20210161
Author(s):  
Lucy Liu ◽  
Gary P. T. Choi ◽  
L. Mahadevan
Keyword(s):  
Systematic Approach ◽  
Building Blocks ◽  
Lattice Structures ◽  
Deployable Structures ◽  
Arbitrary Size ◽  
Mechanical Metamaterials ◽  
Symmetry Properties ◽  
Art Forms ◽  
Wallpaper Groups ◽  
Repeating Patterns

Kirigami, the art of paper cutting, has become a paradigm for mechanical metamaterials in recent years. The basic building blocks of any kirigami structures are repetitive deployable patterns that derive inspiration from geometric art forms and simple planar tilings. Here, we complement these approaches by directly linking kirigami patterns to the symmetry associated with the set of 17 repeating patterns that fully characterize the space of periodic tilings of the plane. We start by showing how to construct deployable kirigami patterns using any of the wallpaper groups, and then design symmetry-preserving cut patterns to achieve arbitrary size changes via deployment. We further prove that different symmetry changes can be achieved by controlling the shape and connectivity of the tiles and connect these results to the underlying kirigami-based lattice structures. All together, our work provides a systematic approach for creating a broad range of kirigami-based deployable structures with any prescribed size and symmetry properties.

scholarly journals Vimentin on the move: new developments in cell migration

F1000Research ◽  
2018 ◽  
Vol 7 ◽  
pp. 1796 ◽  
Author(s):  
Rachel A. Battaglia ◽  
Samed Delic ◽  
Harald Herrmann ◽  
Natasha T. Snider
Keyword(s):  
Cell Migration ◽  
Cancer Cells ◽  
Cell Biology ◽  
Wound Repair ◽  
Molecular Mechanisms ◽  
Epithelial Mesenchymal Transition ◽  
Metastatic Cancer ◽  
Building Blocks ◽  
Mesenchymal Transition ◽  
New Findings

The vimentin gene (VIM) encodes one of the 71 human intermediate filament (IF) proteins, which are the building blocks of highly ordered, dynamic, and cell type-specific fiber networks. Vimentin is a multi-functional 466 amino acid protein with a high degree of evolutionary conservation among vertebrates. Vim−/− mice, though viable, exhibit systemic defects related to development and wound repair, which may have implications for understanding human disease pathogenesis. Vimentin IFs are required for the plasticity of mesenchymal cells under normal physiological conditions and for the migration of cancer cells that have undergone epithelial–mesenchymal transition. Although it was observed years ago that vimentin promotes cell migration, the molecular mechanisms were not completely understood. Recent advances in microscopic techniques, combined with computational image analysis, have helped illuminate vimentin dynamics and function in migrating cells on a precise scale. This review includes a brief historical account of early studies that unveiled vimentin as a unique component of the cell cytoskeleton followed by an overview of the physiological vimentin functions documented in studies on Vim−/− mice. The primary focus of the discussion is on novel mechanisms related to how vimentin coordinates cell migration. The current hypothesis is that vimentin promotes cell migration by integrating mechanical input from the environment and modulating the dynamics of microtubules and the actomyosin network. These new findings undoubtedly will open up multiple avenues to study the broader function of vimentin and other IF proteins in cell biology and will lead to critical insights into the relevance of different vimentin levels for the invasive behaviors of metastatic cancer cells.

scholarly journals Harnessing transition waves to realize deployable structures

2020 ◽  
Vol 117 (8) ◽  
pp. 4015-4020 ◽  
Author(s):  
Ahmad Zareei ◽  
Bolei Deng ◽  
Katia Bertoldi
Keyword(s):  
Energy Harvesting ◽  
Arbitrary Shape ◽  
Three Dimensional ◽  
Building Blocks ◽  
Stable Configuration ◽  
Deployable Structures ◽  
One Dimensional ◽  
Entire Structure ◽  
Significant Interest ◽  
Potential Applications

Transition waves that sequentially switch bistable elements from one stable configuration to another have received significant interest in recent years not only because of their rich physics but also, for their potential applications, including unidirectional propagation, energy harvesting, and mechanical computation. Here, we exploit the propagation of transition waves in a bistable one-dimensional (1D) linkage as a robust mechanism to realize structures that can be quickly deployed. We first use a combination of experiments and analyses to show that, if the bistable joints are properly designed, transition waves can propagate throughout the entire structure and transform the initial straight configuration into a curved one. We then demonstrate that such bistable linkages can be used as building blocks to realize deployable three-dimensional (3D) structures of arbitrary shape.

Photochemical Evolution of Interstellar/Precometary Organic Material

1997 ◽  
Vol 161 ◽  
pp. 23-47 ◽  
Author(s):  
Louis J. Allamandola ◽  
Max P. Bernstein ◽  
Scott A. Sandford
Keyword(s):  
Origin Of Life ◽  
Building Blocks ◽  
Complex Species ◽  
Infrared Observations ◽  
Interstellar Ice ◽  
Polycyclic Aromatic ◽  
Ultraviolet Photolysis ◽  
The Origin Of Life ◽  
Simple Molecules ◽  
Complex Organic

AbstractInfrared observations, combined with realistic laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the building blocks of comets. Since comets are thought to be a major source of the volatiles on the primative earth, their organic inventory is of central importance to questions concerning the origin of life. Ices in molecular clouds contain the very simple molecules H2O, CH3OH, CO, CO2, CH4, H2, and probably some NH3and H2CO, as well as more complex species including nitriles, ketones, and esters. The evidence for these, as well as carbonrich materials such as polycyclic aromatic hydrocarbons (PAHs), microdiamonds, and amorphous carbon is briefly reviewed. This is followed by a detailed summary of interstellar/precometary ice photochemical evolution based on laboratory studies of realistic polar ice analogs. Ultraviolet photolysis of these ices produces H2, H2CO, CO2, CO, CH4, HCO, and the moderately complex organic molecules: CH3CH2OH (ethanol), HC(= O)NH2(formamide), CH3C(= O)NH2(acetamide), R-CN (nitriles), and hexamethylenetetramine (HMT, C6H12N4), as well as more complex species including polyoxymethylene and related species (POMs), amides, and ketones. The ready formation of these organic species from simple starting mixtures, the ice chemistry that ensues when these ices are mildly warmed, plus the observation that the more complex refractory photoproducts show lipid-like behavior and readily self organize into droplets upon exposure to liquid water suggest that comets may have played an important role in the origin of life.

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